Any suggestions on how best to flash or seal replacement Andersen PermaShield patio doors using T-111?

These patio doors will be replacing existing 35 yo Andersen patio doors. The siding in the area is T-111 5/8, which is over 1/2" plywood sheathing and 5/8 foil Celotex. The replacements are fractionally smaller than the existing doors. I have a low ranch house with a 3 foot roof overhang that provides good protection.

The existing doors will have the nailer flange cut off on top and sides. At present there is no additional "flashing" on sides and top except for brick mold trim that overlaps the door and siding. The contractor would use 1x4 pine brick molding and overlap it and caulk it on the siding and door frame on the new doors. The 1" gap between the door jambs and siding / framing opening could be filled and caulked with backer rod. Any suggestions on supplementing the caulked trim with flashing? Thanks.